Rotary screening apparatus for separating different kinds of materials in mixtures



Nov 6, 1962 B. E. PALM 3,062,375

ROTARY SCREENING APPARATUS FOR SEPARATING DIFFERENT KINDS OF MATERIALS IN MIXTURES Filed Oct. 16, 1958 3 Sheets-Sheet 1 W @JWWI Nov. 6, 1962 B. E. PALM 3,062,375

ROTARY SCREENING APPARATUS FOR SEPARATING DIFFERENT KINDS OF MATERIALS IN MIXTURES Filed Oct. 16, 1958 3 Sheets-Sheet 2 Nov. 6, 1962 B. E. PALM 3,062,375

ROTARY SCREENING APPARATUS FOR SEPARATING DIFFERENT KINDS OF MATERIALS IN MIXTURES Filed Oct. 16, 1958 3 Sheets-Sheet 3 3,062,375 Patented Nov. 6, 1962 ROTARY SCREENING APPARATUS non SEPARAT- llN G DIFFERENT KINDS OF MATERIALS IN MIXTURES Bel-til Emanuel Palm, P.0. Box 163, Mobodarne, Sweden Filed Oct. 16, 1958, Ser. No. 767,692 Ciaims priority, application Sweden Oct. 14, 1957 6 Claims. ((11. 209-303) The invention relates to a rotary screening apparatus for separating different kinds of materials forming the constituents of mixtures, especially for separating finer materials from coarser materials in mixtures.

Apparatus of this type are well-known, in which one or generally a plurality of screen drums are arranged to perform a combined movement, viz. a revolving (circulating) movement around a rotation center disposed laterally to the respective screen drum as well as an individual rotary movement around its own axis, wherein the finer material is forced radially through the surrounding perforated surface of each screen drum on account of the centrifugal action of the revolving movement which takes place with a relatively high speed, While the individual rotary movement of the screen drums, which takes place with a relatively low speed, causes .a cleaning or clearing of the screen surfaces of the drum as the sections of said surfaces are successfully turned against said rotation center. Apparatus of this kind having no transport screw means movable relative to the screen drum surface, have the advantage that the wear of the screen surface is essentially reduced. However, the advance of. the coarser material through the screen drums has not been sufiicient, nor was the separation of water from wet mixtures effective. For eliminating these disadvantages it has been suggested to provide the inside of the screen drum surface with helically extending guiding surfaces forming inwardly open spiral channels. These guiding surfaces or channels create some improvement, but because they are entirely open towards the center of the drum they, similar to screen drums without helical guiding surfaces, require a rather high centrifugating speed in order to secure that the material actually passes along the same. Now, in certain cases,,on account of difficulties regarding the supply of material into the drums or in view of the requirement of a soft or delicate treatment, the centrifugating velocity must be very low, but then the open helical channels do not secure an advancing movement of the material in a helical path along the screen surface, but the material will in part. fall axially and straight through the interior of the screen drum. As a typical example of such a case the treatment of paper pulp may be mentioned.

The primary object of the invention is to avoid the ditficulties mentioned above by simple and expedient means, and in particular both securing a positive advance movement of all material in a helical path along the inside of the screen surface and avoiding Wear of the screen surface. Another object of the invention is to facilitate the mounting of the screen drums. A further object is to secure an effective filtering action while preventing the coarser material from intermingling with the finer material.

According to the invention at least one conveyor strip extending helicaily within each screen drum and being firmly connected with the same, has a lateral dimension or width covering substantially the whole distance from the individual axis of the drum to the surrounding screen surface of the same. The axis of the drum is formed by a shaft which preferably extends throughout the entire drum and may be made with a relatively great diameter, and said conveyor strip is firmly connected or engaging both with the surrounding screen surface of the drum and with the shaft and partakes in the individual rotary movement of the drum. Said conveyor will prevent any amount of the mixture from falling straight through the drum in the axial direction of the same, but will force the mixture to move along the helical path also when the centrifugating speed is very low.

The exit ends of the screen drums project through corresponding openings in a disk confining an outlet chamber for coarser material, while finer material is obtained through an annular outlet chamber surrounding the plurality of screen drums.

Thus, the invention will render it possible to select any centrifugating speed, even a very low centrifugating speed, and under the control of the two movements (viz, the revolving centrifugating movement and the individual rotary movement) the helical conveyor strip will cause a positive and exact feeding of the mixture helically along the surrounding screen surface so as to secure an effective filtering action. The possibility of using a low centrifugating speed will also reduce the stresses imposed upon the screen-in surfaces, which for the screening of paper pulp and the like have to be made with a very fine perforation and consequently also of a thin sheet material. In addition, the mounting of the screen drums is facilitated as they are supported by means of the helical conveyor strips.

Further objects of the invention and features of the same will appear from the following specification when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical central cross-section through the apparatus according to one embodiment of the invention;

FIG. 2 is a horizontal diagrammatic cross-section taken along the lines 11-11 in FIG. 1;

FIG. 3 is a horizontal diagrammatic cross-section taken along the lines IIIIII in FIG. 1;

FIG. 4 is a vertical central cross-section similar to FIG. 1 but illustrating a modification;

FIG. 5 is a vertical central cross-section through a screen drum, including modified conveyor means.

In the figures of the drawings the same reference numerals are used throughout for corresponding elements or parts.

In FIG. 1, reference numeral 1 indicates a base member of the frame, upon which a bottom plate 2 is securely mounted. Said bottom plate supports a central stationary sleeve 3 and a cylindrical housing 4, attached to said plate. In the stationary sleeve 3 the upright main shaft 5 is rotatively mounted, said shaft extending vertically through the apparatus and having its lower end connected with transmission means 6, 7 for imparting to the same a rotary movement from a driving motor (not shown).

Between two spaced disks 9 and 10 attached to the main driving shaft 5 a plurality of vertical secondary shafts 11 are rotatively mounted, which secondary shafts support each a corresponding screen drum 12 over a helically extending conveyor strip 13 firmly connected or engaging both with the shaft and the surrounding screen surface. The screen drums 12 may be made of perforated sheet metal, having slots or circular apertures. Several conveyor strips 13 may be disposed in each individual screen drum is a way similar to that of a doublethread screw. The drum shafts 11 extend downwardly through the bottom disk 9 and supports each a respective chain wheel 14 (see also FIG. 3), these chain wheels 14 supporting a chain 15 extending around the plurality of said chain wheels. One of the drum shafts 11 (the righthand one in FIG. 1) has an extension 11' supporting a bevel gear wheel 16 meshing with a bevel gear wheel 17 attached to the end of a horizontal shaft lh mounted for rotation in brackets 119 and 2t). Said brackets are supported by the disk 9 and rotatable with the same. The horizontal shaft 18 supports a worm wheel 21 meshing with a stationary screw thread 22 provided on the stationary sleeve 3. Thus, when the main driving shaft is rotating together with the disks 9, 10, a rotation is imparted to the transmission means 22, 21, 18, 17, 16 for rotating said one drum shaft 11, 11, the rotation of said one drum shaft being transferred to the remaining drum shafts over the chain transmission means 14, 15. The gear ratio should be selected such that the drum shafts rotate more slowly than the main shaft. For instance, the drum shafts could be driven with a speeed of 50 revolutions per minute, while the main shaft is driven with a speed of 800 revolution per minute.

The top disk supports a conical cover 23 having a central inlet 24 for the mixture to be separated, as well as guiding channel-shaped sections 25 for conducting the mixture and distributing the same into the individual screen drums 12. The plurality of screen drums 12 is enclosed by an outer stationary casing 26 supported by the housing 4- and being wider than the same. The casing 26 forms an annular space 27 around the plurality of screen drums, said space constituting an outlet chamber 27 for the finer material obtained through the perforated screen surface of the screen drums 12 and communicating with an outlet conduit 28. The screen drums 12 have their lower ends disposed at some distance above the bottom disk 9, an outlet chamber 29 being formed above said disk for the coarser material obtained through the lower open ends of the screen drums. Said outlet chamber 29 communicates with an outlet conduit 30 for the coarser material, and the bottom disk 9 may be provided with vanes 31 for assisting the rotating bottom disk in moving said coarser materials outwards. Immediately above the lower ends of the screen drums there is provided a disk 32 attached to the main shaft 5 and having openings for the individual screen drums. Said disk 32 forms a partition between the two outlet chambers 27 and 29.

It may be assumed, that a mixture in the form of a suspension of materials of different particle sizes is supplied to the inlet 24 while the screen drums 12 are revolving rapidly around the main shaft 5 and rotating slowly on their own individual shafts 11. The suspension is distributed to all screen drums 12, the finer material being centrifugated out of the screen drum surfaces through the portions which are turned away from the main shaft 5, while clogging material in the portions facing towards the main shaft 5 is removed by the action of the centrifugal force with respect to the main shaft 5. The individual rotation of each screen drum 12 on its own shaft 11 is adapted to successively turn succeeding segments of each screen drum towards the main shaft for being cleaned. The suspension is advanced through each screen drum 12, moving along the associated conveyor strip 13, while the finer material is successively centrifugated out through the perforated surfaces of the screen drums. The coarser material is obtained as a residue at the lower ends of the screen drums. On account of the centrifugal force caused by the revolving (circulating) movement the conveyor strips 13 will have an advancing effect on the material, the finer material being centrifugated out through the perforations while the conveyor strip prevents the same from passing freely in the axial direction, and a definite discharge of the coarser material being secured without intermingling with the finer material.

For separating a plurality of materials of different particle sizes in a mixture, each individual screen drum may be divided in two or more concentric annular spaces by means of one or more intermediate cylindrical screening surfaces, conveyor means or strips being disposed within each such concentric drum and firmly connected with the same. Thus, there is formed, around each individual secondary shaft, a unit comprising several concentric drums. Apparatus of such modified structure are well suited for use as pulp screening apparatus or strainers, as the inner screen surface having apertures of larger size will form a strainer so that a separate strainer is superfluous. By the provision of one intermediate screening surface a high quality pulp may be obtained through the circumference of the outer screening surface, while a second quality is obtained from the annular space around said intermediate screening surface. If two intermediate screening surfaces are provided, the high quality pulp is obtained from the outer one of the two annular spaces, while water together with resins are obtained through the circumference of the outer screen surface which can be made of a rather fine filter material. Thus, the invention will also realize the object of creating an apparatus of a compact construction for performing several different functions.

FIG. 4 illustrates an apparatus incorporating the modified structure stated above, having a plurality of screen drum units or sets, each comprising two concentric screen drums 12' and 12 of different diameter, the inner one 12 having perforations of greater size than the outer one 12". The inner screen drum 12' is supported by the shaft 11 over the conveyor strip 13', and the outer screen drum 12" is supported by the inner screen drum 12 over the conveyor strip 13". Immediately above the lower ends of the inner screen drums 12' the disk 32' extends, which is attached to the main shaft 5 and is provided with vanes 31. The outer screen drum 12" has its lower end disposed at some distance above the disk 32', and a further disk 32" extends immediately above the lower ends of the outer screen drum 12". A stationary cover 35 is disposed on the top of the outer casing 26 and a stationary bearing 36 may be provided for the top end of the main shaft 5, said top end then being extended above the cover 35.

The mixture to be separated is supplied to the inner one of the concentric screen drums, as also indicated in FIG. 4, the finer material passing through the perforations of the respective screen drums, and the coarser material advancing downwards along the respective conveyor strips 13' and 13". Above the disk 9 there is formed the outlet chamber 29 for the coarser material, obtained through the open lower ends of the inner screen drums 12 and discharged through the outlet 30. When using the apparatus for wood pulps or paper pulps such coarser material could be the substances comprising the knots or the like. Above the disk 32 there is formed an outlet chamber 29 for a material of medium particle size, for instance a second quality pulp, which material is obtained through the lower open ends of the annular spaces formed around the inner screen drums 12 after passing through the perforated circumference of the inner screen drum 12', said material being discharged through the outlet 30. The material having the finest particle size, for instance paper pulp of the highest quality, is obtained through the perforated circumference of the outer screen drum 12" and is collected in the outlet chamber 27 to be discharged through the outlet 28.

FIG. 5 illustrates a modification of the conveyor means. As appearing from this figure, the conveyor strip can be interrupted at spaced points along its extension, whereby separate conveyor members 13" are formed, also having guiding surfaces for the material, extending helically and constituting propeller-like transport members. The vanes 13" are firmly connected both with the shaft 11 and with the screen drum 12, for rotating with the same.

It should be understood that the apparatus according to the invention may be utilized for numerous purposes in spite of the simple structure of the same. Thus, as indicated above, it can be used not only for separating finer materials from coarser materials in liquid suspensions, for instance for separating coarser and finer fibres and resins in cellulose pulps (wood pulps or paper pulps), separating the knots or the like from pulps or removing the water from paper pulps or other wet masses, but it can be used also for separating mixtures in the solid 5 state, comprising particles of different sizes, for instance milled or ground mixtures. Further examples of use are in the separation of fatty mixtures in slaughtering yards or houses and in whale cookeries, the separation of oil mixtures, the cleaning or purifying of certain materials, as well as the cleaning of waste water (sewerage).

It should also be understood that the apparatus described above and illustrated in the drawings could be mounted also horizontally or inclined, that is, with a horizontal or inclined driving main shaft, the structure of the apparatus being generally the same.

The embodiments and modifications shown in the drawings and described above are intended to illustrate the invention by way of example and not to limit it other than necessitated by the scope of the appendent claims.

I claim:

1. An apparatus for separating different kinds of materials forming the constituents of a mixture, comprising, a main shaft, means for imparting a rotary movement to said main shaft, a plurality of screen drums disposed around and supported by said main shaft for receiving a revolving movement around the same, shafts each extending axially within one of said individual screen drums, transmission means for imparting an individual rotary movement to each individual shaft of said screen drums, simultaneously with said revolving movement, and at least one conveyor strip extending helically within each of said screen drums and being firmly engaged both with the respective screen drum and with the individual shaft of the same for supporting said respective screen drums from said individual shafts a disc at the ends of said drums to which material therein is conveyed by said conveyor strips, said disc having openings adjacent said drums respectively for discharge of coarser material, and means forming an annular outlet chamber surrounding said drums for receiving finer material separated from the coarser material.

2. An apparatus for separating different kinds of materials forming the constituents of a mixture, comprising, an upright main shaft, means for imparting a rotary movement to said main shaft, screen walls forming a plurality of upright screen drums disposed around said main shaft, shafts each extending axially within one of said individual screen drums, a disk attached to said main shaft below the lower ends of said screen drums and rotatably supporting said individual shafts of said screen drums for causing a revolving movement of said individual shafts around said main shaft, said disk also confining an outlet chamber for material obtained from the lower ends of said screen drums, a second disk attached to said main shaft immediately above the lower ends of said screen drums and an outlet chamber being disposed around said plurality of screen drums for material obtained through the screen walls of said screen drums, transmission means for imparting an individual rotary movement to each individual shaft of said screen drums, simultaneously with said revolving movement, and at least one conveyor strip extending helically within each of said screen drum and being firmly engaged both with the respective screen drum and with the individual shaft of the same for supporting said respective screen drum from said individual shaft.

3. An apparatus for separating different kinds of materials forming the constituents of a mixture, comprising, an upright main shaft, means for imparting a rotary movement to said main shaft, a disk attached to said main shaft, a plurality of secondary upright shafts disposed around said main shaft and rotatably supported by said disk for performing a revolving movement around said main shaft, transmission means for imparting an individual rotary movement to each of said secondary shafts, simultaneously with said revolving movement, at least one conveyor strip extending helically around each individual one of said secondary shafts, and being attached to the same, a

screen drum disposed concentrically around each sec-' ondary shaft and supported by the same for rotation to gether with said conveyor strip, said screen drum having its lower end disposed at some distance above said disk, an outlet chamber being formed above said disk for material obtained from the lower ends of said screen drums,- a second disk attached to said main shaft immediately above the lower ends of said screen drums, at least one further conveyor strip extending helically around eacr individual one of said screen drums and being attached to the same, at least one further screen drum disposed concentrically around each individual one of said first-mentioned screen drums and forming annular space around the same, said further screen drum being supported by said further conveyor strip for rotation together with the same, said further screen drum having its lower end disposed at some distance above said second disk, an outlet chamber being formed above said second disk for material obtained from the lower ends of said further screen drums, a third disk attached to said main shaft immediately above the lower ends of said further screen drums and an outlet chamber being disposed around said further screen drums for material obtained through the circumference of said further screen drums.

4. In apparatus for separating different kinds of materials forming the constituents of a mixture, in combination a plurality of sets of screen drums, means mounting said sets at locations angularly spaced from each other about a central axis from which said sets are spaced radially, each of said sets of screen drums comprising a plurality of drums of different diameters arranged concentrically with each other about common axes, respectively, which are parallel with said central axis, means for imparting to said screen drum sets revolving movement about said central axis, means for imparting to each of said screen drum sets individually rotating movement about their individual axes respectively, simultaneously with said revolving movement, and at least one conveyor surface extending helically within each of said concentric screen drum sets and partaking in the individual rotary movements of said screen drum sets, respectively.

5. An apparatus for separating different kinds of materials forming the constituents of a mixture, comprising, a plurality of screen drums, means for imparting to said screen drums revolving movements around a center located laterally to said screen drums, shafts each extending axially within one of said screen drums, means for imparting to each of said shafts an individual rotary movement around its own axis, sumultaneously with said revolving movement of said screen drums, a plurality of conveyor strips at least one of which extends helically Within each of said screen drums respectively and being firmly engaged both with the surrounding screen surface of said screen drum and with said respective individual shafts of said screen drums for supporting said screen drums from said individual shafts, a disc at the ends of said drums to which material therein is conveyed by said conveyor strips, said disc having openings adjacent said drums respectively, for discharge of coarser material, and means forming an annular outlet chamber surrounding said drums for receiving finer material separated from the coarser material.

6. An apparatus for separating different kinds of materials forming the constituents of a mixture, comprising a plurality of screen drums, means for imparting to said screen drums revolving movements around a rotation center located laterally to said screen drums, shafts each extending axially within one of said screen drums, means for imparting to each of said shafts an individual rotary movement around its own axis, simultaneously with said revolving movement of said screen drums, at least one intermediate screen drum surface disposed concentrically Within each of the surrounding screen surfaces of each of said screen drums for dividing the same in at least tWo concentric spaces, respectively, at least one conveyor strip extending helically within each of said intermediate screen drums and being firmly engaged both with the screen surfaces of said intermediate screen drums and with said individual shafts for supporting said intermediate screen drums from said individual shafts, and at least one further 5 conveyor strip extending helically within the concentric space formed around each of said intermediate screen drums, said further strips being firmly engaged both with said intermediate screen drums and with the surrounding screen drums respectively for supporting the last-men- 10 tioned screen drum from said intermediate screen drum.

UNITED STATES PATENTS Page Nov. 21, 1871 Wiegand June 17, 1884 Savage Feb. 22, 1916 Zelezniak Jan. 5, 1932 Wuensch Mar. 7, 1939 Sinn Feb. 4, 1958 FOREIGN PATENTS France Apr. 30, 1955 

